The article examines the manuscript Calm D 16 in Oirat «clear letter» «Ači üreyin sudur» («Cause and Effect Sūtra») from the manuscript collection of the Library of the Oriental Faculty of St. Petersburg State University. This sutra refers to Buddhist apocryphal (non-canonical) writings, which in some traditions of Tibetan literature were considered to be the untrue «word of the Buddha», and therefore were not always included in the Buddhist canon. Despite the fact that it was translated from Chinese, in Tibetan and Mongolian translations it entered the Kagyur (Ganjur), and was obviously used by Buddhist priests for didactic purposes to educate the lay community. According to the content, the sutra is a conversation between the Buddha and the disciple Ananda, which explains the consequences of good and evil deeds, which are built into a certain system of ethical norms for a lay Buddhist. Positive actions include cultivating compassion, practicing the six paramitas, making offerings to Buddhist temples, stupas, the Three Jewels (Buddha, Dharma and Sangha), as well as to the Teacher and parents, reading aloud, rewriting, contributing to rewriting and reflecting on the Mahayana sutras. Negative actions in the sutra are actions that lead to suffering of living beings: inflicting pain, intimidation, hunting, theft, murder, etc., showing disrespect towards the Three Jewels, the Teacher, the sacred texts of the sutras, the monastic sangha. A comparison of the Oirat translation with the Tibetan and Mongolian canonical versions as part of the Kagyur (Ganjur) shows that the Oirat text is based on either another Tibetan version or an independent revision different from the canonical Mongolian text.